celos23

hi guys well im new to this forum stuff looks good well i have a s1 7 12a turbo it has been rebuilt 4000kms ago its fitted with a big turbo wastegate computer 4 x injectors has extend porting while driving the other day the motor started knocking i was doin 50kmh towed it home compression test was good so removed motor and stripped it down found the rear stationary gear has failed well the teeth are broken same on the rotor the computer is limited to 7800rpm and it ran 12psi also found the center plate is marked on both sides from the rotors rubbing on it ? kind of scored it hasnt been dowelled and is making 370hp i want to fix but dont want the same thing to happen again any ideas thanks



it was fitted with new rotors 1x new housing new gaskets all seals full re build then dyno tuned the shop that did this build is saying i missed a gear and to **** off pretty much im not happy just need more info to fight them thanks marcel just loaded pictures cheers

RONIN FC

Is that the original stationary?

celos23

yes that is the original stationary it has cracks in it they are saying they visually measured up ok are there after market ones available im more concerned about the markings on the center plate thanks

HeffSpooled

You should put a copy or link in the engine building area. I'll bet Lynn would have something intelligent to say about it.



The galling doesn't look all that bad. I have a set with big blue marks. But I'm not sure how much you can get away with.



Welcome to the forum.



Cheers

celos23

thanks i will, center plate coukd be cleaned up just wondering what caused that

Lynn E. Hanover

I am here Grasshopper.





You said the magic word.



Knocking.



That is detonation. While it is very nearly impossible to detonate a Normally Aspierated (NA) rotary (Although my driver can do it) it is quite easy to detonate a turboed rotary.



Detonation is intake charge temperature dependant. There is no more to it. There is only temperature.



I can hear the hair standing up on necks around the world, but wait.



There are a number of items that cause the charge temperature to go over the limit either over a long period, or instantaneously.



The rotary, with a wide space between the plugs and no squish areas is practically designed to detonate.



Detonation is the autoingnition of the mixture remote from the plug(s) and AFTER the planned ignition event.



All you need is a bit of extra heat to start it. You can do it with an actual over temp of some system, like water temp and , or, oil temp, (rotor face temp too high) and intake air temp too high. You can also create the effect by under reving the engine with a load on it. From cruise at low revs just press down the throttle, during a period where another system is already close to critical.



The rotor turning below normal RPM for a particular situation, looks like an accelerated flame front (lower octane fuel) to the engine.



See that in your minds eye. The head space is not getting bigger fast enough to allow for the expanding gasses, and as a result, the pressure (temperature) gets too high, too soon. This would not be a missed shift but a lack of a downshift, when required.



Stationary gear failures from long term over stress (fatigue) tend to just get cracks between the teeth, and can be caught early by checking the magnet on the oil drain plug. You would also see shiny rear main bearing from the stationary gear and crank flexing (ouch).



Parts of teeth coming off without cracks between the teeth is more likely the result of a (number) of high overstress events.



So, what to do?



I have no personal experience with turboed rotarys, so this advice may be crap.



Lower charge temperature.



Induction air from high in the center of the radiator opening. Highest pressure, coolest air.

Program more ignition retard when knock sensor is triggered.

Program a bit richer when boost is up. (over rich and way over lean mixtures mimic higher octane fuel)

Observe RPM before applying throttle, downshift if you will still be below redline after shift.

Add induction water injection.

Lower temp thermostat. Plug the bypass hole and run an American 160 degree stat as God intended.

Add radiator capacity.

Bigger intercooler.

Apply water spray to the intercooler when boost is up.

Bigger oil cooler. Rotors are oil cooled. Oil temps over 160 reduce power output.

If OMP is in use, use a straight weight dino oil. If premixing, Redline racing 2 cycle oil in the fuel, Your favorate Synthetic oil in the sump.

Reduce total boost.

use higher octane fuel.

Use a few extra pounds of torque when doing case bolts.

If that iron is not twisted and can be smoothed with a DA (orbital sander) and silicon carbide paper and light oil.





Lynn E. Hanover

j9fd3s

that would explain why only those teeth (toofs?) are broken.

13BTNOS

Do you have pictures of the gear side of the rotor? Is it possibe that the rotor gear walked on you. And like the previous post from Lynn. Do everything he says! Run a oil cooler and get a bigger radiator. I have a Griffin on mine and is a 2 row with runners being 1.5in yes that would be a total of 3in thick damn thing is nearly as big as my intercooler. LOL. Oil coolers I'd look into a Setrab or Mocal. Stock oil coolers are great but Setrab just my personnel preference. Also get a very good tune. Repeat get a very good tune. It's well worth the money to pay someone who knows what they are doing. Especially when it comes to rotarys and turbos. Unless you yourself have the know how and confidence to do it yourself. Heat is your enemy so fight it off as much as you can. Good luck. And yes they do sell aftermarket hardened stationary gears. I'm assuming your from Aus but there are some shops that are dealers for Racing Beat out there. If not try Guru Motorsports they make "race" stationary gears. But for the most part if it's not getting beat over 8500rpms all day long stock will be fine for you.

TYSON

Can you post more pictures of both gears? Some of the wear on the gear looks pretty strange.

celos23

ill post more piks on monday i just need to get them thanks